1. Field of the Invention
This invention relates to an upsetter for upsetting end portions of elongated work members of steel and like materials.
2. Description of the Prior Art
Known upsetters for upsetting end portions of lengthy work members are largely classified into a vertical type which has vertically split dies as illustrated in FIGS. 1 to 3 and a horizontal type which has horizontally split dies as illustrated in FIG. 4.
As seen in FIGS. 1 and 2, the vertical type upsetter is provided with vertically split dies 1 and 2 which are opened and closed in a horizontal direction by a drive mechanism which is provided at one side of the machine. The upsetter is provided with a U-shaped frame 3 which is open on the upper side and supports on its inner side the above-mentioned dies 1 and 2. In order to prevent the frame 3 from being expanded on the upper open side at the time of gripping a work member 4, a cross tie rod 5 is provided perpendicularly along the upper side of the frame 3.
Therefore, in the vertical type upsetter with the dies 1 and 2 enclosed on four sides as seen in the direction of arrow II of FIG. 2, there invariably arises the necessity of transferring the work member 4 over a relatively large distance to deliver the same to the front side of the machine and for moving the work in longitudinal directions when inserting and extracting it before and after the upsetting operation.
More specifically, as seen in FIGS. 1 and 2, a work member 4 which has its end portion heated in a furnace 6 is transferred horizontally over a certain distance for delivery to the working position of the upsetter as indicated by arrow I and then moved in the longitudinal direction for insertion into the upsetter as indicated by arrow II. Work member 4 which is inserted in the upsetter is then lowered stepwise as indicated by arrow III to undergo primary and secondary upsetting operations in the dies 1 and 2. Upon completion of the upsetting operation, the work member 4 is drawn out of the upsetter by moving the same longitudinally backward over a substantial distance as indicated by arrow IV and then lifted to the initial level as indicated by arrow V, followed by a horizontal movement over a large distance as indicated by arrow VI for transfer to the location of the next operation.
Consequently, the forming operation by a vertical upsetter entails transfer of the heated or upset work member 4 in a horizontal direction as indicated by arrow I or VI within a short time period in addition to substantial longitudinal movements in the directions of arrows II and IV. Namely, it has a drawback in that it requires complicated and costly transfer and handling mechanisms for moving the work in lateral, longitudinal and vertical directions. Besides, there has to be provided a long path of transfer in total to cope with the large breadth of the upsetter including the drive mechanism located at one side thereof, and the transfer of works in three different directions, resulting in a prolonged period of time for one cycle of operation, lower productivity and high production cost.
Especially, in the case of hot forging, the work members cool off while moved along the long path of transfer, so that greater force and energy are required for the upsetting operation and the number of consecutive operations which are possible per single heating is limited. Consequently, due to the difficulty of completing the forming operation with only one heating stage, there arise the necessities of die replacement and reheating of the work members before finishing the upsetting operation.
In order to eliminate these problems, there has been developed a horizontal type upsetter which, as seen in FIG. 4, is provided with a series of horizontally split dies 8 and 9. The dies 8 and 9 are opened and closed in the vertical direction by a drive mechanism which is located over the dies 8 and 9 to reduce the machine width.
As shown in FIG. 4, in the horizontal type upsetter, the work members which are passed horizontally through part of the split dies 8 and 9 are moved back and forth to evade interference with paired pull rods 11 which serve to maintain the gripping force of the dies 8 and 9. That is, the work members which are fed into the machine in a slightly retracted position to avoid the first pull rod 11 are pushed in and fed transversely to undergo sequentially the upsetting operations of the primary and secondary stages in the dies 8 and 9. Upon finishing the upsetting, the work members are retracted again to avoid interference with the second pull rod 11 before they are discharged from the upsetter for transfer to the location of the next operation.
The horizontal type upsetter which has a smaller width needs a shorter path of travel and thus contributes to shortening the cycle time of the upsetting operation and to enhancing the productivity as compared with the vertical type. Another advantage of the horizontal type upsetter resides in the fact that the transfer and handling mechanisms can be simplified to a significant degree as the main transfer routes are all on the same horizontal plane. Further, in contrast to the vertical type the dies of which are closed in a frame on four sides, a horizontal type upsetter permits observation of the conditions of the upset product with the naked eye from three sides when the dies are opened, so that some suitable measures can be taken promptly to remove the cause of any defect as soon as a defective product comes out.
Although the paths of travel of the work members in the horizontal upsetter are arranged two-dimensionally, that is to say, in one horizontal plane, the works have to be moved in longitudinal directions to evade collision against the pull rods 11 which move only a small distance in the longitudinal direction. Namely, there still remains the problem of utilizing a complicated transfer or feed mechanism in the known horizontal upsetter which is not constructed to transfer the works or products along a linear path of travel.
In the upsetters shown in FIGS. 1, 2 and 4, the upset die and clamp die sections of the respective dies are driven integrally so that it is difficult to adjust the clamping force and the upset die closing force independently of each other. Therefore, in order to securely clamp those work members which contain large variations in outside diameter, there should be provided a clearance between the clamp dies, which however gives rise to a problem in that the upset die closing force is varied due to variations in the outside diameter of the work members, resulting in a varying quality of the products.
Further, the die has an upset die section A and a clamp die section B independent of each other as shown particularly in FIG. 3 with hydraulic back-up devices C and D for the respective die sections so that there is a possibility of bending the work members due to a die centering error. In addition, the direct drive system utilizing crank E and F has another problem in that clamping pressures applied on the two dies differ in each clamping stroke by variations in stop position of a brake G. In order to eliminate the variations in clamping force, there has to be provided a hydraulic cylinder of a large stroke length, which however invites a large energy loss and necessitates the use of a clutch H with a large torque characteristic.
The clamp mechanism in either type of the above-described conventional upsetter is usually provided with unitary die holders 14 and 15 on die plates 16 and 17 for holding juxtaposed upper and lower dies 12 and 13, respectively, as seen in FIG. 23 which exemplifies a horizontal type upsetter, applying the clamping pressure by a hydraulic cylinder 19 which is provided in a tong head 18 integrally with the upper die plate 16. Therefore, in the particular example shown, when a couple of tubes which contain variations in outside diameter are simultaneously clamped, one clamp die which receives a tube of a smaller diameter fails to clamp it securely against a sliding deviation as caused by the punch 20 (see FIGS. 2-14) in the upsetting stage, failing to upset the two pipes simultaneously.
Such a clamping failure leads to a degradation of the product quality and to difficulty in the upsetting operation itself especially in the case of oil well tubes which have a relatively large tolerance in outside diameter as compared with other steel workpieces. In addition, the clamp mechanism of the conventional upsetter employs a hydraulic cylinder 19 of a fixed capacity so that it has been impossible to increase the clamping force and thus to adjust the power of the upsetter to a higher level when circumstances require.